Thermodynamic and Structural Properties of the Acid Molten Globule State of Horse Cytochrome c
Thermodynamic and Structural Properties of the Acid Molten Globule State of Horse Cytochrome c
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DOI：
10.1021/bi101806b
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发表时间：
2011-04-19
期刊：
影响因子：
2.9
通讯作者：
Kidokoro, Shun-ichi
中科院分区：
文献类型：
--
作者：
Nakamura, Shigeyoshi;Seki, Yasutaka;Kidokoro, Shun-ichi
为了理解蛋白质的稳定、折叠和功能机制，了解熔融球态的结构和热力学性质是非常重要的。本研究通过溶液x射线散射（SXS）、动态光散射和圆二色性测量，对马细胞色素c在低pH和高盐浓度下的酸性熔融球态（我们称之为MG1）的整体结构进行了评价。用差示扫描量热法和等温酸滴定量热法等热法测定了马细胞色素c在N向MG1和MG1向变性态D转变过程中的热力学参数。测定了N向MG1转变过程中的热容变化δ c -p为2.56 kJ K-1 mol(-1)，表明MG1状态下水化程度有所提高。此外，在低盐条件下，pH为4时马细胞色素c的n - d热跃迁的中间态在SXS和量热测量中表现出与MG1态相同的结构和热力学性质。15℃时n到mg1和n到d转变的吉布斯自由能变化G分别为10.9和42.2 kJ mol（-1）。
To understand the stabilization, folding, and functional mechanisms of proteins, it is very important to understand the structural and thermodynamic properties of the molten globule state. In this study, the global structure of the acid molten globule state, which we call MG1, of horse cytochrome c at low pH and high salt concentrations was evaluated by solution X-ray scattering (SXS), dynamic light scattering, and circular dichroism measurements. MG1 was globular and slightly (3%) larger than the native state, N. Calorimetric methods, such as differential scanning calorimetry and isothermal acid-titration calorimetry, were used to evaluate the thermodynamic parameters in the transitions of N to MG1 and MG1 to denatured state D of horse cytochrome c. The heat capacity change, Delta C-p, in the N-to-MG1 transition was determined to be 2.56 kJ K-1 mol(-1), indicating the increase in the level of hydration in the MG1 state. Moreover, the intermediate state on the thermal N-to-D transition of horse cytochrome c at pH 4 under low-salt conditions showed the same structural and thermodynamic properties of the MG1 state in both SXS and calorimetric measurements. The Gibbs free energy changes (Delta G) for the N-to-MG1 and N-to-D transitions at 15 degrees C were 10.9 and 42.2 kJ mol(-1), respectively.